Electronic instrumentations or communication systems utilize various signal converting techniques to increase or decrease frequencies of electronics signals. For example, a wireless communication device such as a cellular telephone communicates with a base station using microwave or radio frequencies (RF) in the order of hundreds of MHz, tens of GHz, or even higher. However, within the communication device, the RF signal is converted to an intermediate frequency (IF) signal for processing.
To receive information from the base station, the communication device receives RF signal (encoding the information) from the base station. The frequency of the RF signal can be, for example, 10 GHz. Within the communication device, the RF signal is down-converted to IF signal (while preserving the encoded information). Frequency of the IF signal is typically lower than the frequency of the RF signal and can be, for example, 1 GHz. The down-conversion is realized using an image rejection mixer (IRM). Then, the IF signal is further processed to extract the information.
To transmit information to the base station, the communication device encodes the information on IF signal of, for example, 1 GHz. Then, the IF signal is up-converted to RF signal (while preserving the encoded information and rejecting a local oscillator signal) of, for example, 10 GHz. The up-conversion is realized using a local oscillator signal rejection up-conversion mixer also refereed to as a local oscillator signal rejection mixer or an up-conversion mixer.
The image rejection down-conversion mixer (the image rejection mixer, IRM) and the up-conversion mixer (UPM) of the communication device is typically optimized to operate at a particular RF and IF frequencies. For example, the IRM can be designed to convert 10 GHz RF signal to 1 GHz IF signal, and the UPM can be designed to convert 1 GHz IF signal to 10 GHz RF signal.
In the current IRM and UPM designs, efficiency of operation of the mixers depends heavily on the operating frequency. In fact, a typical single-ended FET mixer-based IRM or a UPM has a relatively narrow bandwidth of approximately 10 percent of its designed frequency. That is, for example, a typical single-ended FET mixer-based IRM designed to operate with a 10 GHz input RF signal and 9 GHz local oscillator (LO) signal has acceptable efficiencies of operation with an input RF signal having frequency ranging from approximately 9.5 to 10.5 GHz for RF signal and 8.5 to 9.5 GHz for LO signal. Outside these frequency ranges, the IRM is too inefficient for practical use.
Likewise, a typical single-ended FET mixer-based UPM designed to operate with a 1 GHz input IF signal and 10 GHz output RF signal has acceptable efficiencies of operation with an input IF signal having frequency ranging from approximately 950 to 1050 MHz and output RF signal of 9.5 to 10.5 GHz. Outside this frequency ranges, the UPM is too inefficient for practical use.
Efficiency of a mixer such as the IRM and the UPM is calculated as conversion loss ratio. The conversion loss ratio is a ratio of the amplitude (representing the power or strength) of its output signal to the amplitude (representing the power or strength) of its input signal.
In some applications such as for instrumentation or electrical warfare (EW) applications, it is desirable for a mixer (down-conversion or up-conversion) to have high efficiency of operation for a wide range of input frequencies, or wide bandwidth. The present mixer designs (IRM and UPM) with its narrow bandwidth are not suitable for these applications. There is a need for wider bandwidth conversion mixers.